The aims of this project for the currently funded period employed genetically engineered mouse lines. The overarching goal of these studies was to elucidate neurobiological mechanisms that contribute to an increased vulnerability to alcohol use disorders, with a focus on both hippocampal/amygdala GABAergic synaptic transmission (Aims 1-2) and epigenetics (Aim 3). As noted in earlier progress reports, some methodological challenges were encountered in re-establishing the breeding colonies of global and conditional Kl mice. Because of the delays in establishing the needed mouse lines, Aims 1&2 will continue essentially as originally described into the extension phase. Studies of the epigenetic effects of ethanol (Aim 3) will continue to focus on characterizing the effects of ethanol on histone modifications in mice following acute and chronic ethanol exposure and following ethanol withdrawal. The provocative discovery by the PI of transgenerational alterations in ethanol-induced behaviors and drinking following paternal preconception ethanol exposure has provided a need to significantly expand the experimental focus of this grant in an exciting new direction. Our results suggest that an individual's ethanol phenotype is dictated in part by his father's history of ethanol exposure prior to conceiving that individual. Remarkably, these transgenerational effects of ethanol appear to only affect male offspring. These exciting observations suggest that ethanol is an epimutagen (i.e., it alters the epigenetic program) that impacts germ cells in an enduring fashion. To further investigate the hypothesis that an individual's drinking and neurobiological sensitivity to ethanol are due in part to parental preconception ethanol exposure, we will (1) characterize the model in greater detail, (2) undertake studies to reveal the mechanism(s) that mediate these effects, (3) examine if these effects represent true transgenerational epigenetic inheritance, (4) develop a rat model of paternal preconception ethanol exposure, and (5) conduct neurobiological studies to better understand the phenotype.